1. Field of the Invention
This invention relates to locking mechanisms for tape cassettes.
2. Description of the Prior Art
The method used to prevent conventional video tape cassette wheels from rotating while not working is dependent on serrations around the peripheries of the tape wheels, a moving unit that can be inclinedly moved only upwards, two fixing arms that can be moved by said moving unit and two springs set respectively on said fixing arms for automatically pushing back said fixing arms. When the tape cassette is not put into the tape recorder or the rewinder, the moving unit stays at the normal position and the fixing arms, by means of their springs, mesh with the serrations of the tape wheels preventing the tape wheels from idle rotation. On the contrary, when the tape cassette is put into a recorder or a rewinder, the lifting rod of the recorder or the rewinder will push the moving unit upwards, and the fixing arms, being moved by the moving unit, are caused to be separated from the serrations of the tape wheels so that the tape wheels may be set loose for free rotation.
However, the above mentioned design of conventional locking tape wheels still has the disadvantages listed as follows.
1. The locking design for the cassette wheels is based on mutual movement among five parts interconnected by a passive and indirect transmission. They perform a double-armed synchronous action which causes their complicated structure, and their production cost runs high because five parts need separate molds in manufacture. PA1 2. The operational action is not quite accurate because of its indirect action operated by five parts used in a round-about transmission. PA1 3. Since each of the fixing arms performs an independent synchronous action, if either of the two springs is fatigued or out of order, the fixing capability will be lost immediately.
Conclusively, the conventional locking mechanism for a video tape cassette is not only complicated in structure but has a high cost, because it includes quite a few of parts which are rather complicated in manufacture and are easy to get lost owing to their small sizes and have a high percentage of malfunctioning. Besides, their actions are not direct. Therefore it is necessary to improve such a tape cassette for both manufacturers and users.